I gotta say, at idle that thing sounds like thunder, it was nearly shaking my house from my sound system connected to my desktop computer. Very unique sound IMHO, a big block with basically open pipes and a cam from the sound of it.
Loooong time ago I'd seen a few of these in other swaps. They would have a few problems with the final drive on the 325s. You need to add an adapter plate to flip the final drive and that shortens the amount of shaft into the pinion. If you used the 325c overdrive/4 speed 82-85, a little work was needed to the overdrive drum to take the extra horses. Reversing was the best way to go to keep as much iron in front of the wheels but they are still about 60/40 over the axle. Can you say wheely bars? With that much weight in the back, it is hard to get the front to grab well on hard turns. Anything other than dry pavement, with sticky tires, they want to keep going straight when you try to do a quick turn. Even seen pics of a non reversed in the front of a VW rabbit. The 72-76 specs were underated due to EPA and insurance expectations. With little work they all could be upped. Mostly exhaust and intake. It has been an extreme amount of time since I had looked at any real numbers. If my memory serves me right, the 73 with forged, scalloped weights cranks and 71-72 heads were the best for building. Never did like the stock caddi exhaust manifolds and headers were rare and expensive.
[This message has been edited by cmechmann (edited 11-04-2013).]
Actually, the differential is flipped, therefore causing the axles to turn in the opposite direction. Simple design actually. Check out the picture and you can see how it's set up.
Oh okay.... I always like the 425 setup.... I'm old enough to remember the old Tornados and Eldorados from the 60s when they were new. I built models of them just to see how the transmission looked, but I never knew the differential could be flipped and reverse the whole setup. That's really cool.
A few years ago those engines and trans were a dime a dozen at Pick Your Pat, there all gone forever now. Buick, Olds, and Pontiac 455's too. Buick and Pontiac 455's were kind of rare but could be found with patience. Big block Chevys they never had at Pick Your Part. I did see two and both times guys were pulling them.
Olds Toronado brings back some memories. Grandpa had a 1976 with a 425 cui in it if I recall, he was complaining about the poor gas mileage and gas was at the unheard price of......... $1.75 gallon. So dad swapped in a Iron Duke 151 cui. Well it worked ok, but when Grandpa took it in to the Firestone Service Center for an oil change. The mechanic popped the hood and said WTF is that? I got the impression that mechanics don't like working on engine swapped cars.
The TH425 would take more abuse, but there is a limit in the flipped design and 3 gears. The TH325c that came out of a 82-85 Riviera 3.8 turbo already has the beefed up clutch drums and 4 gears. That flipped with a GN 3.8 would also help with the weight problem. But still have a stub of a shaft into the the final drive compared to the the stock setup.